The Conservatives estimate their plan would cost £6bn a year in 2029-30, based on Oxford Economics’ analysis.
The party says it has identified £71bn in annual savings including £36bn a year from welfare cuts.
Prof Andy Summers, director of the Centre for the Analysis of Taxation, told BBC Verify this was “just about about the worst possible way to deliver an inheritance tax cut”.
“Exempting the family home however much it’s worth will just encourage older people to concentrate their savings in their home, prevent downsizing, and so further gum up the housing market,” he said.
The Conservatives argue in their press release accompanying the policy announcement that inheritance taxes are “bad for growth”.
But analysis by the Organisation for Economic Co-operation and Development suggests inheritance taxes in general are less damaging to economic growth than taxes on income from work.
Additional reporting by Nicholas Barrett
